1. Field of the Invention
This invention relates to a processing program falsification preventing method in a sheet processing apparatus having an equipment main body which inspects sheets such as securities or banknotes and performing a sealing process or cutting process according to the inspection result, and a management device which is connected to the equipment via a USB cable to manage the equipment.
2. Description of the Related Art
The equipment includes a main controller which controls the whole portion of the equipment, a sub controller which controls a process such as a feeding process other than the inspecting process, a plurality of sub detectors for inspecting, and a main detector which determines the inspecting result according to the detection contents from the sub detectors.
Further, as the management device, a general purpose personal computer (PC) is used.
Conventionally, when the program is checked, a request for hash function value calculation of the program is issued from the PC to the main controller. Then, the main controller issues the request for hash function value calculation to each CPU of the main controller, sub detector and main detector and collects and returns the hash function values calculated by the CPUs to the PC. The PC calculates hash function values for the programs of the respective CPUs which are previously provided therein and compares the thus calculated hash function values with the hash function values transmitted from the main controller. Then, the PC determines that the program is not falsified by detecting that the compared hash function values are coincide with each other.
A system of SHA1 is used for calculation for hash function values and the hash function value attained has 160 bits. Since the original (program) cannot be formed based on the hash function values and it is extremely difficult to form the same hash function value, it is possible to determine that the program is not falsified if the hash function values coincide with each other.
When the hash function value is calculated based on the program in the CPU, it takes ten-odd seconds to calculate the hash function value since the program size is one MB or more.
Therefore, there occurs a problem that it takes a long time to check the program.
Further, in the above example, the hash function values which are collectively returned to the PC are always set to the same value and a problem in security occurs.